“Maybe I should have kept that one,” Trout joked with reporters a few days later.

Trout’s card sold in August, shortly after the market for modern cards went into overdrive. In September, two months after the James rookie card sold for $1,845,000, a Giannis Antetokounmpo rookie card produced by Panini fetched $1.9 million. Antetokounmpo is 26, with barely eight seasons in the N.B.A. and a full career ahead of him.

“The modern cards are taking the market by storm,” said Chris Ivy, the director of sports at Heritage Auctions. “The vintage market is very strong, too, but the modern cards have joined in.”

Of the top 10 prices paid for sports cards at public auction, seven were cards of modern stars who were playing as recently as 1999, and five of the 10 cards have players pictured who are still active. The list, however, is ever changing. A rising star card in the collectibles world is an immaculate so-called Logo Man card of Zion Williamson and Ja Morant (the top two picks from the 2019 N.B.A. draft). It can be had on eBay for a cool half a million dollars — just click on “Add To Cart.”

“The industry is at its hottest point in my 40-year history,” Ken Goldin, the founder of Goldin Auctions, said in an email. “It is nearly impossible to keep up with demand from buyers.”

Ivy said that with the coronavirus pandemic shutting down many businesses, the sports collectibles industry expected hard times, too. But the opposite happened.

“It’s not something I saw coming,” he said. “We, like many businesses, were tightening our belts preparing for a potential downturn, but the fact that we’ve seen so much interest and so many people jumping in the market is a bit surprising.”

Credit…Fred R. Conrad/The New York Times

And the market continues to boil. Earlier this month, a 1997 Michael Jordan card fetched $1.4 million at auction. The soaring prices have created such a frenzy that investment groups are being formed to buy cards, making it harder for individual collectors to compete — even extraordinarily wealthy ones.